The phrases Body, Packet, and Section exist to create abstractions from what one layer is liable for verses the others.
To elucidate that, and to reply your query totally, I’ll begin a bit “earlier” than what you’re actually asking.
Due to this fact…
- When Layer 4 will get knowledge, it provides to it a header which facilitates service to service supply like TCP or UDP ports (amongst different issues) — this complete datagram is known as a Section.
- When Layer 3 will get knowledge, it provides to it a header which facilitates finish to finish supply just like the supply IP of the preliminary sender and the vacation spot IP of the ultimate recipient — this complete datagram is known as a Packet.
- When Layer 2 will get knowledge, it provides to it a header which facilitates hop to hop supply just like the Supply and Vacation spot MAC addresses of the present “hop” within the community — this complete datagram is known as a Body.
The is basically the method of Encapsulation, illustrated on this animation:
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A Body then, is the L2 header plus no matter knowledge must be delivered to the subsequent hop:
-
Body:
[L2 HDR][110011001010101011110000...010101] -
You and I do know that contained in the body is a L3 header and a L4 header and utility knowledge, however so far as L2 is worried, every little thing inside is only a collection of
1s and0s that have to be delivered to a different hop. -
A Packet then, is the L3 header, plus no matter knowledge must be delivered to the opposite finish:
-
Packet:
[L3 HDR][1010101011110000...010101] -
You and I do know that inside the packet is a L4 header and utility knowledge, however so far as L3 is worried, every little thing inside is only a collection of
1s and0s that have to be one other endpoint -
A Section then, is the L4 header, plus no matter knowledge must be deliverred to the opposite service:
-
Section:
[L4 HDR][11110000...010101] -
You and I do know that inside the Section is the applying knowledge which is to be processed by the receiving service
And the applying knowledge itself, after all, goes to vary with each utility. HTTP for net requests, FTP for file transfers, and so forth.
The time period Datagram itself is solely the assemble of a header and bits. And the phrases above are merely the distinctive names for the actual Datagram that operates at every layer.
- A Body is the Datagram at L2
- A Packet is the Datagram at L3
- A Section is the Datagram at L4